ALZHEIMER'S disease progresses faster in people who are highly educated, research suggested.

Past studies have found that high levels of education may help ward off the dementia caused by Alzheimer's.

But new research, published in the Journal of Neurology Neurosurgery and Psychiatry, found that high educational attainment may also speed up the progression of Alzheimer's once it has developed.

The team, from Columbia University Medical Centre in New York, studied 312 patients over the age of 65 who had all been diagnosed with Alzheimer's.

These New Yorkers were monitored for five years, undergoing various assessments of brain function.

The researchers, led by Dr Nicolaos Scarmeas, found that the overall mental agility of all the patients declined every year.

But for each extra year of education the patients received, there was an additional 0.3% deterioration.

The speed of thought processes and memory appeared to be particularly affected by higher levels of education.

The researchers said: "We found a faster rate of cognitive (mental) decline in patients with higher educational attainment compared to those with lower education.

Memory

"This association was particularly noted in the specific domains of executive speed and memory."

The researchers said their findings remained the same even when other factors such as age, depression and vascular disease, which are likely to affect brain function, were taken into account.

The team said that one possible explanation for the results was something known as "cognitive reserve" theory.

Thie theory suggests that the brain's ability to cope with Alzheimer's varies between different people.

The amount of nerve connections (neurons) and information hubs (synapses) are likely to be more numerous in people who are highly educated.

The theory also suggests that even if the quantity of neurons and synapses is the same, the synapses are likely to be more efficient and alternative circuitry is likely to be working in those with higher education.

Therefore higher educational levels mean that the brain develops the decreased mental agility of Alzheimer's later than in some people because these brains are able to tolerate the changes caused by the disease for longer.

But when the disease does develop the impact is likely to be greater than in less educated brains because it has a higher level of accumulated damage.